Some image forming apparatuses form images using toner. A developing device supplies toner toward an image bearing member (photoconductor drum) on which an electrostatic latent image has been formed, thereby developing the electrostatic latent image. A toner containing body (toner container) is mounted in such an image forming apparatus in order to supply toner to the developing device to replenish the developing device with toner. Furthermore, in some cases a hopper, which relays a replenishment of the toner from the toner containing body to the developing device, is provided between the toner containing body and the developing device. Some image forming apparatuses detect the amount of toner in the hopper. Such image forming apparatuses are known.
Specifically, in such an image forming apparatus, a developing section and a toner cartridge are arranged side by side in the lateral direction. The developing section develops a latent image on the image bearing member using toner, and the toner cartridge supplies the toner with which the developing unit is replenished. The toner cartridge is removably mounted in the image forming apparatus. A communication opening and a control valve are provided between the toner cartridge and the developing section. The communication opening allows the toner to pass therethrough, and the control valve controls the amount of the toner allowed to pass through the communication opening. The developing section includes a toner transportation paddle and toner detection means. The toner transportation paddle having a comb-shaped film and a rectangular film drives the control valve, and the toner detection means, which is provided below the control valve, detects the toner. With the above-described structure, a state in which the amount of the toner has decreased to a certain level due to being used in a developing hopper is reliably estimated, and, when the developing hopper runs short of the toner, use of any more toner is prohibited, thereby preventing the quality of images from being degraded and a developing unit from being damaged.
In general, the toner replenishment device stores a large amount of toner in order to allow printing to be continued to some extent even when the toner container has run out of toner. When the toner replenishment device runs short of toner, the toner replenishment device is replenished with toner from the toner container.
However, when an excessive amount of the toner is fed into the toner replenishment device, the toner may overflow out of the toner replenishment device and contaminate the interior of the image forming apparatus. In order to suppress such an issue, detectors are provided in some cases. Such a detector contacts the toner in order to detect that the amount of the toner in the toner replenishment device has reached a specified amount and the toner replenishment device has been sufficiently (to such an extent that no overflow of the toner occurs) replenished with the toner.
In some toner replenishment devices, an agitating member (agitating paddle) that rotates so as to agitate and transport the toner is provided. In general, in order to entirely agitate the toner without leaving part of the toner unagitated, it is preferable that the agitating member agitate as large an area as possible. However, depending on the rotation angle of the agitating member, the agitating member may block a path of the toner from a toner receiving port, through which the toner supplied from the toner container is received, to the detector of the toner.
It is assumed that the toner receiving port is arranged, for example, on an upper surface of the toner replenishment device. In this case, when the position of the agitating member is above the detector so as to overlap the detector (when the agitating member is at such a position that the agitating member covers the detector like an umbrella), the toner from the toner container does not reach the detector. Thus, there is a problem in the event that the amount of the toner in the toner replenishment device has reached a specified amount but, depending on the rotation angle of the agitating member, cannot be detected. Particularly, when the amount of the toner in the toner replenishment device has reached the specified amount but cannot be detected, replenishment of the toner to the toner replenishment device from the toner container may be continued until the toner overflows out of the toner replenishment device.
Here, the toner detection means of the developing section of the image forming apparatus estimates a state in which the remaining amount of the toner has decreased, and does not detect that the developing section has been sufficiently replenished with the toner in an amount by which the toner in the toner replenishment device has reached the specified amount.